Mr. Fox also suggested that marijuana is a safe alternative to opioid painkillers. In reality, the best studies show that marijuana is effective only for a specific type of pain (neuropathic), which opioids do not treat well. Further, non-addictive medications that are superior to marijuana in treating neuropathic pain are available.

Perhaps most misleading, Mr. Fox implied that marijuana protects brain function and should therefore be freely available to pro football players who sustain head trauma. A recent 38-year study documented a decrease in chronic cannabis users’ IQ.

If the NFL lifts its ban on marijuana, it should not do so because of its purportedly non-addicting, pain-controlling and neuroprotective effects.

Samuel T. Wilkinson, New Haven, Conn.

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When will policymakers realize that the prohibition environment, which produces dangerous drug dealers who “push” harder drugs on their marijuana customers, is the so-called gateway, not the plant itself? Regulation and control remove marijuana buyers from the dangerous environment of the illicit street-corner drug trade, placing them in safe retail stores, and provide the safest-quality marijuana. If you want fewer marijuana users using other drugs, collapse the profitable marijuana-prohibition environment. There is only one way to do that: Legalize it.

Neill Franklin, Silver Spring

The writer, a retired Maryland State Police narcotics commander, is executive director of Law Enforcement Against Prohibition.

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In the Jan. 12 Outlook commentary “If you’re white, feel free to smoke up,” Stacey Patton and David J. Leonard say they are “not ready to celebrate the most recent moves to decriminalize marijuana” in Colorado because some states have decriminalized (but not legalized) marijuana but still have disparate rates of incarcerated black men.

Users caught with marijuana are often issued civil fines or ordered to undergo treatment. In some jurisdictions that have decriminalized marijuana, police will arrest users on technicalities, such as the presence of paraphernalia, and those arrests often disproportionately affect people of color.

Colorado’s law is the first legalization law in the nation. Before it passed, there were 10,000 marijuana possession arrests in Colorado each year. Now anyone age 21 or older can purchase, possess and privately use marijuana free of interference by the police. This also means police cannot claim the smell or view of marijuana in order to racially profile.

Instead of criticizing the voters of Colorado, Ms. Patton and Mr. Leonard should commend them for taking a step in the right direction.